Irreversible COX Inhibitors

Question 1

Give an example of an irreversible COX inhibitor

Answer 1

Aspirin

Question 2

What is the mechanism of action of aspirin?

Answer 2

• Irreversibly inhibits COX

- Irreversibly inhibits thromboxane A2

Question 3

What is COX involved in?

Answer 3

Prostaglandin release

Question 4

What is thromboxane A2 needed for?

Answer 4

Platelet aggregation

Question 5

What is the result of the inhibition of thromboxane A2?

Answer 5

Prevents blood from clotting and forming thrombus

Question 6

What is the route of delivery of aspirin?

Answer 6

PO

Question 7

What are the indications for aspirin?

Answer 7

• Treatment of MI
• Prophylaxis of MI
• Pregnant women at high risk of pre-eclampsia

Question 8

How is aspirin given in the treatment of MI?

Answer 8

Usually as 300mg stat dose

Question 9

How is aspirin given in the prophylaxis of MI?

Answer 9

Usually 75mg OD

Question 10

When is aspirin used in pregnant women at high risk of pre-eclampsia?

Answer 10

Can be taken from week 12 to delivery

Question 11

What are the contraindications to aspirin?

Answer 11

• Patients on anti-platelet drugs, e.g. clopidogrel
• Patients at high risk of bleeding, e.g. haemophiliacs
• Peptic ulceration
• Known hypersensitivity to aspirin or NSAIDs
• Children under 16

Question 12

Who should aspirin be used with caution in?

Answer 12

• Asthma
• Anaemia
• Elderly
• During 3rd trimester of pregnancy

Question 13

What might aspirin interact with?

Answer 13

• NSAIDs
• Anticoagulants
• SSRIs

Question 14

What are the side effects of aspirin?

Answer 14

• May induce bronchospasm in asthmatics
• Peptic ulceration
• GI bleeding
• Tinnitus
• Nasal polyps

Question 15

What can be done to prevent peptic ulceration with aspirin?

Answer 15

PPI may be co-prescribed

Question 16

When might the side effects of tinnitus and nasal polyps occur with aspirin?

Answer 16

At analgesic doses, which may be higher than dose used for secondary prevention of cardiac events

Question 17

What counselling is required with aspirin?

Answer 17

• How to take aspirin
• Prolonged bleeding
• Not for children

Question 18

How should aspirin be taken?

Answer 18

Non-dispersible aspirin should not be chewed. Should be swallowed whole with food, and indigestion remedies should be avoided at the time of aspirin consumption

Question 19

What should the patient be told regarding prolonged bleeding?

Answer 19

Aspirin may cause a patient to bleed more or to bleed longer if they sustain an injury. Such symptoms should be reported to the patient’s GP

Question 20

Why should aspirin not be given to children under 16?

Answer 20

Due to risk of causing Reye’s syndrome